1. Field of the Invention
The present invention relates to beams used in the construction of screen enclosures that enclose pools, patios and other outdoor facilities (wherein purlins are often used in roofs to avoid closely spaced rafters), more particularly to a system and method of preparing residential and commercial screen enclosures using box beams for structural wall and roof support that each have a two-piece construction from identical extruded parts, which are preferably either self-mating and joined with fasteners, or snap-fitted together without fasteners. Each extrusion has a generally U-shaped configuration, with a planar central member and two side pieces each depending in substantially perpendicular orientation to the central member. Each extrusion further comprises an interior gusset-retaining slot formed between the planar central member and an exterior spline groove on each side piece, wherein slots positioned in opposed relation to one another are configured to receive and support a precisely cut and tight-fitting gusset plate, which provides more precise beam construction and enhanced (more precise and stronger) joint reinforcement for wall and roof beams positioned in end-to-end relation. Two gusset plates are used in each present invention structural joint, with each gusset plate partially inserted into both beams in the structural joint and secured to the aligned planar central members on opposing sides of the beams via fasteners. Although several fasteners are typically used to secure the present invention tight-fitting gusset plates to the beams in a structural joint, fewer fasteners are used than would otherwise be needed in prior art beams constructed without the structural benefit of present invention interior gusset-retaining slots (saving both labor and material expense). Also, the opposed slots in present invention box beams allow for the joining of two roof beams in a manner that does not interfere with the placement of fasteners in roof purlins. Box beams formed by present invention construction are strong and easy to construct, and thus preferred over prior art box beams in the front walls and roof designs of gable, mansard, dome, and flat screen enclosures. In addition, the tight-fitting gusset plates supported in part by the opposed interior slots of present invention beams provide more precise joints, which allows the construction and joining of such beams to be accomplished with more accuracy and efficiency, and also results in greater screen enclosure strength. Advantages of the present invention system and method include, without limitation, stronger construction of aluminum beams, and tailored construction of aluminum beams to an exact fitted specification which greatly reduces the likelihood of construction error and also results in consistently better-quality and stronger screen enclosure joints. Furthermore, the improved and stronger joint component of the present invention provides a consistent graduation in strength from one beam to another and efficient use of the box beam metal. Consequently, screen enclosures made from present invention box beams are stronger, and able to withstand higher winds and better resist damage as a result of impact from external forces, than screen enclosures made from other box beams currently used in the industry.
2. Description of the Related Art
Screen enclosures are commonly used in both residential and commercial applications to enclose pools, patios and other outdoor facilities. Such screen enclosures generally start as a frame constructed from different types of aluminum beams. To complete the enclosure, screening is stretched over the frame, and screening edges are secured to the structural beams using flexible splines and the spline grooves pre-formed into the exterior surface of the structural beams. Screen enclosures are also constructed in accordance with various local building codes, and when applicable may include additional means of structural reinforcement (such as but not limited to tensioned cables).
Generally, the construction of screen enclosures involves considerable difficulty, and requires extensive experience and skill. With respect to the aluminum structural members that are currently and commonly used for the upright wall beams and roof beams in prior art screen enclosures, such beams typically consist of two identical extrusions joined together via self-mating construction and multiple fasteners to form a generally rectangular box beam configuration. However, precision in the construction of such box beams is often lacking, which results in considerable room for frequent (and sometimes serious) error during screen enclosure construction, and may potentially lead to construction delay, compromised strength in a finished screen enclosure, and/or other screen enclosure deficiencies. In addition to imprecise beam construction, prior art methods used to create structural joints in screen enclosures are also a source of construction error and reduced screen enclosure strength. Since the gusset plates used in the prior art are smaller in dimension than the interior surface of a box beam to which it becomes attached, installers generally estimate its positioning relative to the box beam before attaching fasteners (most commonly screws). However, even when a slight difference in gusset plate positioning exists from one beam to the next, and particularly when the differences are varied and repeated in many of the structural joints in a screen enclosure, such imprecision in gusset plate positioning will provide less than optimal strength in a finished screen enclosure, and reduced enclosure resistance of the screen enclosure to wind and impact damage. Also, since the beams in prior art screen enclosure construction are solely bound together via the fasteners securing two gusset plates between them, the graduation in strength from one prior art beam to another is inconsistent and results in the metal being used inefficiently, and further places all of the stress in the joint on the fasteners. As a result, a relatively weak fastening component is provided when compared to the slot/fastener alternative provided in the present invention. Thus, a need exists for improved beams (stronger and more precisely constructed) to use in the assembly of screen enclosures, and for an improved method of joining beams during the construction of aluminum screen enclosures that enhances their strength and durability, instead of diminishing it.